Oracle REPLACE Function – limitations? ORA-01460

Is there a limitation to Oracle’s REPLACE function? I’m trying to use it to replace a username & password in a html/text file (read in with utl_file) with a username & password provided as parameters.

But I get the following:

ORA-01460: unimplemented or unreasonable conversion requested

However, if the file read in is shorter, it works just fine.